This invention relates to a new method for the preparation of 1,1,2-trichloro-2,2-difluoroethane.
The compound 1,1,2-trichloro-2,2-difluoroethane has been prepared in the past by a variety of methods. These methods include the thermal chlorination of CClF.sub.2 CH.sub.3 and CHF.sub.2 CH.sub.3, the reduction of CClF.sub.2 CCl.sub.3 with isopropanol, and the fluorination of CCl.sub.3 CHCl.sub.2 with antimony fluoride. Except for the fluorination of CCl.sub.3 CHCl.sub.2 and the reduction of CClF.sub.2 CCl.sub.3, 1,1,2-trichloro-2,2-difluoroethane was not the major product and yields were generally poor. The fluorination of CCl.sub.3 CHCl.sub.2 suffers as a method of preparing 1,1,2-trichloro-2,2-difluoroethane because it involves corrosive HF and produces a hazardous, antimony-containing waste stream. The reduction of CClF.sub.2 CCl.sub.3 is not a satisfactory method of making 1,1,2-trichloro-2,2-difluoroethane, due to the fact that CClF.sub.2 CCl.sub.3 is simply 1,1,2-trichloro-2,2-difluoroethane which has been overchlorinated.
In view of the deficiencies of the aforementioned known processes, it would be highly desirable to provide a process having a high selectivity to 1,1,2-trichloro-2,2-difluoroethane without having the problems associated with the methods of the prior art.